Around 5pm on 5/17/18 Angelica turned off the gap cleaning to see the effect this had on the STAR backgrounds.
This was done in two steps:    Around 5:10 the yellow gap cleaning was turned off.   At 5:36 the blue was turned off. 

The results indicate that the source of the background in STAR is a perturbation of the opposite beam's gap cleaning.   The blue gap cleaning causes activity in the yellow abort gap and vice-versa.

The run 19137047 (ending at ~5pm) showed a small amount of background triggered in the blue abort gap, and a lot of background triggered in the yellow abort gap:

The 19138048, started after the yellow cleaning was stopped shows the background in the blue gap disappear

This run continued into the period where ALL of the gap cleaning was off, but does not distinguish the period before and after the blue gap cleaning was ended.   However, when I look at the actual time of the events in the yellow gap we see that they stop exactly at the point where the blue gap cleaning stops.